[submodule] Update submodule sonic-gnmi to the latest HEAD automatica…

…lly (#21375)

#### Why I did it
src/sonic-gnmi
```
* b017531 - (HEAD -> master, origin/master, origin/HEAD) Fix roles checking if cname not exist (#339) (20 hours ago) [ganglv]
* 3afc927 - Better modularization for gnoi_client.go (5 days ago) [Dawei Huang]
|\ 
| failure_prs.log skip_prs.log 6059b18 - finish package sonic module. (6 days ago) [Dawei Huang]
| failure_prs.log skip_prs.log 6867664 - finish packaging system module. (6 days ago) [Dawei Huang]
| failure_prs.log skip_prs.log 1f77986 - seperate util and system module. (6 days ago) [Dawei Huang]
| failure_prs.log skip_prs.log 35df113 - seperate flags into a package config. (6 days ago) [Dawei Huang]
| failure_prs.log skip_prs.log 1405cd2 - format and naming clean up for gnoi_client.go. (7 days ago) [Dawei Huang]
* aa547ad - Improve GNMI service to limit API access by role (#335) (6 days ago) [ganglv]
```
#### How I did it
#### How to verify it
#### Description for the changelog